Regions
Northwest Inland.
Uncertainty about how deep persistent slabs will react to the recent snow and rain warrants a conservative approach to terrain.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
SATURDAY: Cloudy with isolated flurries, moderate southeast winds, alpine temperatures around -8.SUNDAY: Mix of sun and cloud with some isolated flurries, light southeast winds, alpine temperatures around -8.MONDAY: Clearing with a mix of sun and cloud, light west winds, alpine temperatures around -10.
Avalanche Summary
On Thursday, loose dry avalanches were reported in the alpine and loose wet avalanches were reported below treeline. Storm slabs sitting on a weak layer of surface hoar and/or a crust are likely easy to trigger at higher elevations. Full depth avalanches will continue to be a concern for some time due to the weak faceted lower snowpack.
Snowpack Summary
Last week's storm delivered 20-30 cm in the Smithers area and 40 cm or more in deeper areas to the north and west. Freezing levels reached up to 1600 m, leaving moist surface snow which is now freezing into a crust. Storm slabs may be lingering at higher elevations and may sit on a weak layer of surface hoar and/or old hard wind slabs. Most areas continue to have a shallow and weak snowpack that is about 120-150 cm at treeline. In general, the lower snowpack consists of old hard wind slabs above weak faceted snow.
Problems
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.